Functions

1. Unit 2—Lesson 2:
Functions

2. Functions
tieMyShoes()
makeBreakfast(food: "scrambled eggs", drink: "orange juice")

3. Defining a function
Functions
func functionName (parameters) -> ReturnType {
// Body of the function
}
func displayPi() {
print("3.1415926535")
}
displayPi()
3.1415926535

4. Parameters
func triple(value: Int) {
let result = value * 3
print("If you multiply (value) by 3, you'll get (result).")
}
triple(value: 10)
If you multiply 10 by 3, you'll get 30.

5. Multiple parameters
Parameters
func multiply(firstNumber: Int, secondNumber: Int) {
let result = firstNumber * secondNumber
print("The result is (result).")
}
multiply(firstNumber: 10, secondNumber: 5)
The result is 50.

6. Return values
func multiply(firstNumber: Int, secondNumber: Int) -> Int {
let result = firstNumber * secondNumber
return result
}

7. Return values
func multiply(firstNumber: Int, secondNumber: Int) -> Int {
return firstNumber * secondNumber
}
let myResult = multiply(firstNumber: 10, secondNumber: 5)
print("10 * 5 is (myResult)")
print("10 * 5 is (multiply(firstNumber: 10, secondNumber: 5))")

8. Argument labels
func sayHello(firstName: String) {
print("Hello, (firstName)!")
}
sayHello(firstName: "Amy")

9. Argument labels
func sayHello(to: String, and: String) {
print("Hello (to) and (and)")
}
sayHello(to: "Luke", and: "Dave")

10. External names
Argument labels
func sayHello(to person: String, and anotherPerson: String) {
print("Hello (person) and (anotherPerson)")
}
sayHello(to: "Luke", and: "Dave")

11. Omitting labels
Argument labels
print("Hello, world!")
func add(_ firstNumber: Int, to secondNumber: Int) -> Int {
return firstNumber + secondNumber
}
let total = add(14, to: 6)

12. Default parameter values
func display(teamName: String, score: Int = 0) {
print("(teamName): (score)")
}
display(teamName: "Wombats", score: 100)
display(teamName: "Wombats")
Wombats: 100
Wombats: 0

13. Lab: Functions
Unit 2—Lesson 2
Open and complete the exercises in Lab - Functions.playground

14. © 2017 Apple Inc.
This work is licensed by Apple Inc. under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license.